Filter Insert and Filter Device

ABSTRACT

A filter insert has a filter element with an end surface at an inlet side and an end surface at an outlet side that are spaced from one another in a main flow direction of the filter insert. A frame circumferentially extends about lateral sides of the filter element. An axial seal is supported on the frame and has a sealing direction in or opposite to the main flow direction. When inserted into a filter housing and contacting a sealing surface of the filter housing, the seal separates seal-tightly the inlet and outlet. The frame has on two opposite lateral sides of the filter element contact surfaces for clamping the filter insert by matching clamping elements. The contact surfaces are oriented opposite to the sealing direction and each have an individual profile of varying height extending along the two opposite lateral sides.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119 of foreign patent application 10 2009 049 170.8 filed in Germany on Oct. 12, 2009, and which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The invention concerns a filter insert that comprises a filter element with an end surface at the inlet side and an end surface at the outlet side that is spaced from the end surface at the inlet side in the main flow direction. The filter insert further comprises a frame circumferentially extending about the lateral sides of the filter element and connected to the filter element. The frame supports an axial seal whose sealing direction is oriented in or opposite to the main flow direction wherein the seal in the sealing direction can be contacted with a sealing surface of a filter housing so that the inlet side of the filter insert can be separated seal-tightly from the outlet side. On two opposite sides of the filter element the frame has a first contact surface and a second contact surface for clamping the filter insert by means of a first clamping element and a second clamping element. The contact surfaces are substantially oriented opposite to the sealing direction. The contact surfaces each have a profile with varying height.

The invention further concerns a filter device that comprises a filter insert as described and a filter housing with an inlet area and an outlet area for the medium to be filtered.

DE 198 49 089 A1 discloses a filter, especially for the intake air of internal combustion engines, that comprises a housing with a raw air inlet and a clean air outlet as well as a filter element arranged in the housing, wherein the filter element substantially consists of a star-shaped filter material and wherein the housing is of a two-part or three-part configuration and is comprised of a cylindrical housing wall, a detachably connected cup and a cover at the clean air side. WO2008/080129 A1 discloses a filter insert comprising a frame that on two sides has several planar and slanted sections. A variable use with respect to different types of filter elements and filter media is not proposed.

It is therefore an object of the present invention to provide filter devices of the aforementioned kind that are designed to be variable in a controlled fashion, especially such that for variants of filter elements the same housing configuration can be used and at the same time it can be ensured that only filter elements having certain properties can be used.

SUMMARY OF THE INVENTION

In accordance with the present invention, this is achieved in that the filter insert comprises:

a filter element with an end surface at the inlet side and an end surface at the outlet side wherein the direct connection of the end surface at the inlet side and the end surface at the outlet extends in the macroscopic main flow direction especially relative to the filter device as a whole;

a frame circumferentially extending about the lateral sides of the filter element and connected to the filter element, wherein the frame supports an axial seal whose sealing direction is oriented in or opposite to the main flow direction, wherein the seal in the sealing direction can be contacted with a sealing surface of a filter housing so that the inlet side of the filter insert can be separated seal-tightly from the outlet side;

wherein the frame in the area of one of the end surfaces has on two opposite lateral sides of the filter element a first contact surface and a second contact surface for clamping the filter element by means of a first clamping element and a second clamping element;

wherein the contact surfaces are substantially oriented opposite to the sealing direction;

wherein the contact surfaces each have an individual profile of varying height extending along the lateral sides.

The invention further concerns a filter insert, especially intake air filter insert for internal combustion engines, especially for use in a filter device according to the invention, comprising:

a) a filter element with an end surface at the inlet side against which in particular the raw air flow is guided and an end surface at the outlet side where filtered air leaves the filter element in operation;

b) a frame that extends circumferentially about the lateral sides of the filter element that are not flowed through and that is connected to the filter element and has an axial seal, wherein the axial seal can be pressed against a sealing surface of a filter housing in a sealing direction, wherein the frame on two opposed lateral sides of the filter element has a first contact surface and a second contact surface for clamping the filter insert in a filter housing by means of a first clamping element and a second clamping element, respectively, wherein the normals of the contact surfaces are oriented substantially perpendicular to the sealing direction, wherein the first contact surface has a first profile of varying height and the second contact surface has a second profile of varying height that differs from the first profile of varying height, wherein the filter insert especially by means of two clamping elements can be clamped in the housing, wherein the clamping elements each have a counter profile relative to the first and second profiles of varying height.

The sealing direction is in this connection the direction in which the axial seal is to be pressed against a sealing surface in order to generate a sealing action.

Filter inserts according to the present invention have the advantage that for different such filter inserts, for example, provided with different filter media and therefore having different performance characteristics in regard to dust capacity, differential pressure, moisture resistance and flame resistance, individual frames and corresponding individual clamping elements can be provided wherein for all variants the same housing configuration can be used.

In this way, with minimal expenditure variants of filter devices can be made available for which the same housing can be used wherein for each variant an individual combination of frame geometry and geometry of the clamping elements can be employed.

Advantageously, in this way for defined application purposes, it can be ensured by predetermining the shape of the clamping elements that only filter elements with certain properties can be employed.

For example, for a certain internal combustion engine whose intake air is to be purified by the filter insert, it can be ensured according to the invention that only filter elements with filter media can be used that have a satisfactory moisture resistance for the designated use. Accordingly, a simple adaptation of working machines and drive devices to different sites of use and conditions of use is made possible wherein an optimal filtration performance can be achieved for the environmental conditions in question, respectively.

It is especially advantageous that the adaptation of the filter device to the respective boundary conditions can be realized directly at the site of use wherein only the clamping elements must be adapted.

In one embodiment the sealing direction is oriented in the main flow direction, i.e., the seal is pressed in the main flow direction. In an alternative embodiment the sealing direction is opposite to the main flow direction.

In one embodiment, the height of the profile of varying height is defined by the spacing of the respective contact surface section from the plane that is defined by the seal of the filter insert.

In one embodiment, the profile of varying height has at least two adjoining sections wherein one section is extending at an angle to the end surface of the outlet side and the adjoining section extends parallel to the end surface of the outlet side of the filter insert. In addition, or as an alternative, sections with non-continuous slant such as circle sectors or parabola sectors or other curve shapes can be used.

In one embodiment, the profiles of varying height have a common preferred direction along two oppositely positioned lateral sides of the filter element and the height predominantly ascends along the preferred direction wherein the ascent is continuous or takes place in several steps or across several sections.

According to one embodiment, the preferred direction defines the mounting direction of the filter insert into a filter housing.

In one embodiment, the frame in the area of the first and/or the second lateral side has at least one groove for positioning the filter insert during assembly. This groove extends parallel to the plane that is defined by the seal between this plane and the contact surface and undercuts in a direction opposite to the preferred direction a part of the profile of varying height.

This groove has the advantage that, by interaction with a tongue that is formed by a rib on a sidewall of the filter housing, the filter insert when inserted into the filter housing is guided in an optimal position inside the filter housing at the end of the insertion process so that canting or turning of the filter element is prevented.

Moreover, the groove for certain filter insert variants may be provided only at a certain side so that additional variants with different filter housings are enabled whose geometry, by elimination of the ribs, can be adjusted accordingly in a simple way. For example, for applications that require moisture resistance it is possible to principally provide a rib on a particular side while at the same time filter inserts that are not moisture resistant never have a groove on said particular side. At the same time, by means of the different geometries of frame and clamping elements also a differentiation of further properties such as flame resistance etc. can be achieved.

According to a further embodiment, the frame is arranged in the area of the end surface at the inlet side or the end surface at the outlet side and is connected to or monolithically formed with an annular end disk that covers the end surface partially in an outer area and has a flow-through opening allowing passage of flow therethrough wherein on the end disk, inside the seal. an annular rib that extends partially or completely in the circumferential direction is arranged that projects away from the end disk and intersects the surface that is defined by the engagement (sealing) surface of the seal when in the unclamped state. The annular shape can be circular or elliptical or oval.

The circumferentially extending rib is formed in this connection such that it is immersed into an opening of the housing and is surrounded by the opening wherein the opening is arranged inside the sealing surface of the housing.

This has the advantage that upon insertion of a filter insert the seal will not contact, or only slightly contact, the sealing surface of the filter housing across a large initial portion of the insertion travel so that it is prevented that particles that adhere in the area of the sealing surface on the inner housing wall will become detached by the seal upon insertion of the filter insert and reach the clean side of the filter device.

In an advantageous further embodiment the rib that extends annularly is provided with an increased height in the area that is facing the housing lid so that this area penetrates farther into the opening inside the sealing surface of the filter housing than the remaining area. When mounting the filter insert in overhead position from the bottom to the top in a filter housing, the raised portion is supported in the opening as soon as the filter insert is completely inserted into the filter housing and prevents the filter insert from falling out. In this way, the assembly is facilitated because the filter insert and a subsequently attached housing lid that secures the filter insert can be mounted sequentially without having to secure the filter insert manually in position.

Alternatively, the circumferentially extending rib can also be arranged outside of the seal; in this case a recess or groove must be provided in the filter housing outside of the sealing surface.

In one embodiment, on the frame a first and a second guiding projections are arranged so as to adjoin the contact surfaces and, in the mounting direction, extend past the annular surface defined by a vertical projection of the seal.

The guiding projections interact with a ramp that is provided in the interior of the filter housing on the two lateral walls, respectively, wherein the ramp surfaces of the ramp are oriented in a direction of a receiving area wherein the spacing of the ramp surface to the receiving surface decreases in the mounting direction, wherein the guiding projections on the frame upon insertion of the filter insert can be guided by the ramp surface in the direction toward the sealing surface so that the filter insert is positioned such that the rib of the housing can engage the groove of the filter insert.

This has the advantage that the filter insert upon insertion is guided stepwise with increasingly diminished possible play into its end position without the guiding action producing an increased resistance by friction. Moreover, at the beginning of the assembly process no great precision is required for the placement of the filter insert. Moreover, the risk of canting of the filter insert upon insertion is reduced and the filter insert is pre-positioned such that the clamping elements must not overcome a large distance between the loose position in the completely inserted state and the working position in the clamped and seal-tight state.

In one embodiment, the filter insert has at its lateral sides in the area of the end opposite the frame at least two spacer knobs of elastic material. They are designed advantageously such that in the mounted state a no-vibration support of the filter insert in the filter housing is achieved.

The filter insert according to the invention can have different types and shapes of filter elements.

In one embodiment, the filter element has at least one annular star-shaped folded filter medium wherein the end faces of the filter medium form the end surfaces at the inlet and outlet sides of the filter element.

In an advantageous embodiment, the filter insert has two annular star-shaped folded filter medium bellows wherein the smaller filter medium bellows is arranged concentrically in the larger filter medium bellows wherein the frame in the area of a first end surface is connected seal-tightly to the larger filter medium bellows. In the area of the first end surface the interior of the smaller filter medium bellows is completely closed off or sealed, and in the area of the second end surface the end faces of the two filter medium bellows are seal-tightly connected to one another.

In this connection, the outer filter medium bellows in one embodiment can be flowed through from the exterior to the interior and the inner filter medium bellows from the interior to the exterior. In this embodiment, the frame and the seal of the filter insert are located in the area of the end surface of the filter element at the outlet side. Alternatively, the opposite flow direction is possible also.

In one embodiment, the filter element is a compact air filter element with a plurality of passages that are alternatingly closed off in the area of the end surfaces, especially formed by alternatingly positioned layers of a flat filter medium and a corrugated filter medium.

In one embodiment, the filter element is a rectangular zigzag-folded filter element wherein the end surfaces of the filter element are formed by the fold edges.

The invention concerns furthermore a filter insert with a filter medium and an end disk wherein on the end disk a circumferentially extending axial or radial seal is arranged and the end disk comprises a circumferentially extending rib of the kind explained above in paragraphs [0022] to [0025]. Further configurations of this filter insert result from combinations of the individual features set forth in the following.

On the frame at the level of the end disk a first guiding projection and a second guiding projection are arranged projecting in the mounting direction.

On the lateral sides of the filter insert in the area of the end opposite the frame at least two spacer knobs of elastic material are arranged.

The filter element comprises at least one annular star-shaped folded filter medium.

The filter element has two annular star-shaped folded filter medium bellows wherein the smaller filter medium bellows is arranged concentrically in the larger filter medium bellows, wherein the frame in the area of a first end surface is seal-tightly connected to the larger filter medium bellows. In the area of the first end surface, the interior of the smaller filter medium bellows is completely closed off or sealed and, in the area of the second end surface, the end faces of the two filter medium bellows are seal-tightly connected to one another.

The filter element is a compact air filter element with a plurality of passages that are closed off alternatingly in the area of the end surfaces.

The filter element is a rectangular zigzag-folded filter element wherein the end surfaces of the filter element are formed by fold edges.

The invention further concerns a filter device, comprising a filter insert as disclosed above and a filter housing with an inlet area and an outlet area for the medium to be filtered wherein the inlet area or the outlet area has a receiving area with an annular sealing surface that matches the seal of the filter insert.

In one embodiment, on one housing side a mounting opening is provided through which the filter insert is insertable into the filter housing in a mounting direction that is perpendicular to the main flow direction. In this connection, the mounting opening is closable by a lid, in particular in a seal-tight fashion, wherein on the lid two clamping brackets are arranged that project into the filter housing, wherein the first clamping bracket extends along the first lateral side of the filter insert and the second clamping bracket extends along the second lateral side of the filter insert. The clamping brackets have clamping surfaces that are oriented in the direction toward the receiving area, wherein the clamping surfaces each have a profile of varying height and wherein the profiles of varying height of the clamping surfaces match the corresponding profiles of varying height of the contact surfaces arranged on the frame and form a mating shape to these contact surfaces. When the lid is mounted and the clamping brackets project completely into the filter housing, the clamping brackets apply a force onto the corresponding contact surfaces of the filter insert in such a way that the seal of the filter insert is forced against the sealing surface of the housing and the filter insert is therefore secured within the housing.

In one embodiment, two expanded housing sections are provided in the housing sidewalls and are furnished with planar support surfaces that are facing in the direction toward the receiving area. On the planar support surfaces of the housing extensions, the two planar support surfaces of the clamping brackets are supported that are located opposite the clamping surfaces.

In one embodiment of the filter device, in the filter housing at least one rib is provided that is arranged on one of the lateral sides of the filter housing and extends, beginning at the bottom of the filter housing, in the direction toward the mounting opening. The rib is designed such that it engages the groove of the filter insert upon mounting of the filter insert in the filter housing.

In one embodiment, the interior of the filter housing has a ramp at both housing sidewalls, respectively, whose ramp surface is facing toward the receiving area, wherein the spacing of the ramp surface to the receiving surface decreases in the mounting direction. Upon mounting of the filter insert, a guiding projection of the end disk can be guided by the ramp surface in the direction toward the receiving area so that the filter insert is positioned such that the rib of the filter housing can engage the groove of the filter insert.

In one embodiment, the mounting opening is cut deeper into the sidewall of the filter housing on the side of the receiving area where the frame of the filter insert is received as compared to the area of the other end surface of the filter insert.

In one embodiment, the mounting opening at the inlet side is delimited by a bow member on which is arranged a tilting rib projecting into the interior that is contacted by the filter insert when it is tilted within the housing. In this way, it is prevented that the filter insert when being removed will catch on the bow member.

In one embodiment, the filter housing has inside the sealing surface an opening wherein the opening is designed such that, when the filter insert is completely inserted in the mounting direction into the filter housing, the opening surrounds the annular rib that extends partially or completely in the circumferential direction on the end disk of the filter insert.

The invention concerns moreover a product group of filter devices comprising housing variants with lid variants and filter insert variants of filter inserts according to the invention, wherein different filter elements have correlated therewith a combination of the following feature variants, respectively:

a. the groove of the filter insert is provided on none of, on one of, or on both of the filter insert sides;

b. the rib of the filter housing is provided on none of, on one of, or on both of the filter housing sidewalls;

c. at least one of the clamping surfaces and the matching contact surface of the filter insert have a profile of varying height that differs from the profile of varying height of other filter devices of the product group.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an embodiment of a filter insert according to the invention.

FIG. 2 shows a filter housing of a filter device according to the invention.

FIG. 3 shows a lid of a filter housing of a filter device according to the invention.

FIG. 4 shows a partial section view of an embodiment of the filter device according to the invention with a cyclone arrangement.

FIG. 5 shows a section of the filter insert according to the invention.

FIG. 6 shows a further section view of a filter insert according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 and FIG. 5 show an embodiment of the filter insert 1 according to the invention. In this embodiment, on the end surface 3 of the filter element 6 at the outlet side a frame 4 is arranged that supports an axially acting seal 5. The filter element 6 is comprised of two star-shaped folded annular filter medium bellows 6 a and 6 b. The filter medium bellows 6 a, 6 b each have an oval cross-section with two straight parallel sections positioned opposite one another. A smaller filter medium bellows 6 a is concentrically arranged within the annular space that is enclosed by the larger filter medium bellows 6 b such that between the filter medium bellows 6 a and 6 b a flow passage 7 is provided for the medium to be filtered that is passing through the filter device.

In the area of the end surface 3 at the outlet side of the filter element 6 the flow passage 7 provides the outflow opening of the filter element 6 while at the end surface 2 at the inlet side the two bellows 6 a, 6 b are seal tightly connected with one another. The interior of the smaller filter medium bellows 6 a is closed off seal-tightly in the area of the end surface 3 at the outlet side by an end disk or a similar structural element.

In this way, the larger filter medium bellows 6 b is flowed through from the exterior to the interior and the inner filter medium bellows 6 a from the interior to the exterior.

In this way, by means of the filter insert 1 a deflection of the flow is achieved wherein the flow deviates from the main flow direction 8 that is defined by the connection of the end surface 2 at the inlet side to the end surface 3 at the outlet side.

The frame 4 surrounds in the area of the end surface 3 at the outlet side the lateral sides of the filter element 6 wherein the frame 4 by means of four projecting members extending along the straight (or only slightly curved) lateral sides 9 of the filter element 6 has a rectangular cross-section.

Along the straight lateral sides 9 of the filter element 6 the frame 4 has a contact surface 10, respectively, for clamping the filter insert in a filter housing wherein the contact surfaces are oriented opposite to the sealing direction and opposite to the main flow direction 8.

The contact surfaces 10 have along the lateral sides 9 a profile of varying height wherein the contact surfaces 10 in some areas of the profile of varying height have, relative to the surface, a perpendicular that is not parallel to the main flow direction 8 but is positioned at an angle thereto. In the illustrated embodiment the profile of varying height has planar sections that extend parallel to the end surface 3 at the outlet side and moreover slanted sections that extend along the straight lateral sides 9 in the mounting direction at a positive slant wherein the height or the spacing of the contact surface 10 to the end surface 3 at the outlet side increases.

The mounting direction thus defines a preferred direction along which the height primarily increases.

The contact surfaces 10 are designed such that they can be brought into contact with clamping elements in a filter housing. The clamping elements have a profile of varying height matching that of the profile of varying height of the contact surfaces so that in the mounted state a positive locking action between the profiles of varying height is realized.

The two profiles of varying height along the straight lateral sides 9 of the filter element 6 differ in their geometry such that on the two sides a clamping element with a different matching shape must be employed, respectively.

In one embodiment of the filter insert according to the invention, the contact surface comprises several slanted and planar sections arranged in a step-like fashion alternatingly and sequentially behind one another. This has the advantage that only at the end of the insertion process the corresponding planar sections of the contact surfaces of the filter insert and of the clamping surfaces of the clamping brackets rest against one another. In this way, the force required for clamping the seal is produced only at the end of the insertion process. In this way, a minimal required force expenditure for mounting the filter insert is achieved. Moreover, the distance across which the surfaces rub against one another is minimal so that the risk of fusing by friction is minimized.

In one embodiment, the planar sections of the contact surface 10 on either side of the filter element 6 can be arranged stepwise at the same height but at different positions along the mounting direction.

Beginning at the end of the frame 4 that is leading in the insertion direction 11 grooves 28 are arranged on the frame 4 that extend parallel to the plane that is defined by the seal 5 between the end surface 3 at the outlet side and the contact surfaces 10. These grooves 28 can be engaged by a rib 29 provided at the housing in the form of a tongue so that the risk of canting upon mounting of the filter insert is reduced.

At the end surface 3 of the filter element 6 at the outlet side the frame 4 forms an end disk 12 that covers the end face of the larger filter medium bellows 6 b. On this end disk 12 the axially acting seal 5 is arranged whose shape matches the outer contour of the larger filter medium bellows 6 b. Inside the seal 5 a circumferentially extending annular rib 13 is provided that projects axially away from the end disk 12 and extends at especially identical spacing relative to the seal 5 about the flow passage 7. At the end of the frame 4 that is leading in the insertion direction 11 the annular rib 13 is lowered and at the opposite end the annular rib 13 is raised relative to the remaining area. In this connection, the rib 13 projects past the seal 5 with the areas that are not lowered. The plane that is defined in the undeformed state by the engagement surface of the seal 5 is thus intercepted by the circumferentially extending rib 13.

In one embodiment of the invention, the frame 4 at the end of the filter insert trailing in the insertion direction 11 has two protrusions 14 that extend opposite to the main flow direction away from the end disk 12 and have a greater spacing from the straight lateral sides 9 or their imaginary extension than the adjoining areas of the frame 4. These protrusions 14 serve for guiding the clamping brackets upon insertion of the filter insert such that the clamping brackets are inserted straight and without canting. Moreover, the protrusions 14 may prevent in particular mounting of the filter insert in a direction opposite to the intended insertion direction of the filter insert.

The end faces of the filter medium bellows 6 a, 6 b at the inlet side are seal-tightly connected to one another by means of an end disk 15 of flexible material, for example, foamed PUR (polyurethane) wherein the end faces are completely sealed. This end disk 15 has in the area of the straight lateral sides 9 as well as in the area of the ends of the filter insert spacer knobs 16 that are monolithically and integrally formed on the end disk 15 and ensure a flexible vibration-resistant support of the filter insert in a housing.

FIG. 2 shows a filter housing 17 of a filter device according to the invention. In the upper area the filter housing has a mounting opening 18 through which the filter insert 1 in the mounting direction 11 is inserted from top to bottom. The mounting opening 18 illustrated in FIG. 2 is closable by the lid 19 illustrated in FIG. 3. In the housing 17 two expanded housing sections 20 are provided into which the clamping brackets 21 connected to the lid 19 can be inserted. The clamping brackets 21 have clamping surfaces 22 that each have a profile of varying height that can be brought into positive locking engagement with a profile of varying height of the corresponding contact surfaces 10 of the filter insert 1; the corresponding profiles of varying height each form relative to one another a mating shape. In the illustrated embodiment, the profiles of varying height each have slanted and straight sections that rest against one another in the mounted state.

In one embodiment, the mounting opening 18 is delimited at the inlet side by a bow member 38 that is provided with a tilting rib 37 projecting into the interior; the filter insert 1 will contact the titling rib 37 when it is tilted within the housing. In this way, it is prevented that the filter insert can be caught on the bow member 38 upon removal.

The expanded housing sections 20 are provided on the side opposite the sealing surface 23 with planar support surfaces 24 on which the clamping brackets 21 are supported with matching planar support surfaces 25. In the interior that adjoins the sealing surface 23 the mounting opening 18 is recessed downwardly, i.e., in the mounting direction, in order to enable easy insertion of the filter insert 1 in tight spaces. In an alternative embodiment, the support surfaces 24 at the housing and the corresponding support surfaces 25 of the clamping brackets 21 may also have one of the profiles proposed for the clamping surfaces

In the main flow direction 8 inside the sealing surface 23 and adjoining the latter there is a mounting space 26 for a secondary air filter element 33. The opening of the mounting space 26 is embodied with respect to its geometry such that it can receive the circumferentially extending rib 13 of the filter insert 1 and surround it with a gap of in particular a width of 1-5 mm. A loosely inserted, not yet clamped filter insert is prevented in this way from falling out in case of an overhead arrangement.

The clean air outlet 27 adjoins the mounting space 26.

FIG. 4 shows a partial section of an embodiment of a filter device according to the invention wherein the filter insert is clamped and secured, i.e., the seal 5 has been compressed upon insertion of the clamping brackets 21 in that the clamping brackets 21 provide a support action along the contact surfaces 10 of the filter insert and the support surfaces of the expanded housing section 20.

The ribs 29 at the housing engage with play the grooves 28 of the frame 4. Upon insertion of the filter insert into the housing 17 at the beginning of the insertion process the seal 5 is kept at a distance from the sealing surface 23 in that the circumferential rib 13 is resting on the sealing surface 23 in the upper area of the sealing surface 23. Upon further insertion the movement play that is available to the filter insert, for example, by the recessed mounting opening 18, is limited in order to prevent canting of the filter insert. This is achieved in that the guiding projections 31 provided on the frame 4 and extending in the insertion direction 11 impinge on at least one guide ramp 32 that moves the filter insert 1 upon further insertion shortly before the end of the insertion process in the direction toward the sealing surface 23. Subsequently, the ribs 29 of the housing 17 engage the grooves 28 of the frame 4 wherein, on the one hand, the freedom of movement of the filter insert is limited to such an extent that the probability of canting of the filter insert in the housing 17 is reduced but, on the other hand, sufficient play is available in order not to press the seal prematurely against the sealing surface; this reduces the risk of folding or canting of the seal 5. At the end of the insertion process the raised portion of the circumferential rib 13 engages the mounting space 26 of the secondary air filter element and prevents in this way, in case of overhead mounting, the filter insert from falling out before the lid is mounted.

After prepositioning the filter insert 1 the lid 19 can be mounted wherein the clamping brackets 21 first are guided by the protrusions 14 so that the risk of canting of the clamping brackets 21 is reduced. As soon as the clamping surfaces 22 of the clamping brackets 21 come into contact with the contact surfaces 10 of the filter insert, the filter insert is moved in the direction toward the sealing surface 23 and the seal 5 is pressed against the sealing surface 23 so that the raw side of the filter device is seal-tightly separated from the clean side of the filter device.

In one embodiment the filter device comprises a pre-separator at the inlet side, as shown in FIG. 4. The pre-separator comprises a two-part cyclone block 30 that comprises several small individual cyclones.

FIG. 6 shows a further section view of an embodiment of a filter insert according to the invention in a filter device according to the invention along a section line that is modified relative to FIG. 4. In the mounting space 26 shown in section a secondary filter element 33 is arranged that has a circumferential radial seal that clamps the secondary filter element 33 in the mounting space in a fluid-tight way. The circumferential rib of the filter element 1 engages the mounting space 26. Moreover, it is apparent that the seal 5 is pressed against the sealing surface in the sealing direction wherein, in this embodiment, the sealing direction corresponds to the main flow direction 8.

While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles. 

1. A filter insert comprising: a filter element with an end surface at an inlet side and an end surface at an outlet side, wherein said end surface at said inlet side and said end surface at said outlet side are spaced from one another in a main flow direction of the filter insert; a frame circumferentially extending about lateral sides of said filter element and connected to said filter element; an axial seal supported on said frame, wherein said seal has a sealing direction in or opposite to said main flow direction and, when inserted into a filter housing and contacting a sealing surface of the filter housing in said sealing direction, said seal separates seal-tightly said inlet side from said outlet side; said frame having on two opposite ones of said lateral sides of said filter element a first contact surface and a second contact surface for clamping the filter insert by a first clamping element and a second clamping element; said first and second contact surfaces substantially oriented opposite to said sealing direction; said first and second contact surfaces each having an individual profile of varying height extending along said two opposite lateral sides.
 2. The filter insert according to claim 1, wherein a height of said profiles of varying height is defined by a spacing of sections of said first and second contact surfaces from a plane defined by said seal.
 3. The filter insert according to claim 2, wherein said profiles of varying height along said two opposite lateral sides have a common preferred direction along which said profiles of varying height extend and across which said height primarily increases, wherein the increase of said height is continuous or stepwise.
 4. The filter insert according to claim 3, wherein said preferred direction is a mounting direction of the filter insert for insertion into the filter housing.
 5. The filter insert according to claim 3, wherein said two opposite lateral sides are substantially planar or slightly elliptical.
 6. The filter insert according to claim 3, wherein said frame in an area of said two opposite lateral sides has at least one groove that extends parallel to a plane defined by said seal between said plane of said seal and said first and second contact surfaces and undercuts in a direction opposite to said preferred direction a portion of said profile of varying height.
 7. The filter insert according to claim 1, wherein said frame comprises an annular end disk and is arranged at said end surface at said inlet side or said end surface at said outlet side, wherein said annular end disk covers partially said end surface and provides a flow-through opening, wherein said seal is arranged on said annular end disk, wherein said annular end disk has an annular rib that extends partially or completely circumferentially within an area of said annular end disk inside said seal, wherein said annular rib projects away from said annular end disk and intercepts a surface that is defined by an engagement surface of said seal in an unclamped state of said seal.
 8. The filter insert according to claim 7, wherein said frame at a level of said annular end disk has a first and a second guiding projections that project in a mounting direction of the filter insert.
 9. The filter insert according to claim 7, wherein said filter element has at least two spacer knobs of elastic material on said lateral sides at an end opposite said frame.
 10. The filter insert according to claim 1, wherein said filter element comprises at least one annular star-shaped folded filter medium.
 11. The filter insert according to claim 1, wherein said filter element comprises a first and a second annular star-shaped folded filter medium bellows, wherein said first filter medium bellows is smaller than said second filter medium bellows and is arranged concentrically inside said second filter medium bellows, wherein said frame is seal-tightly connected to said second filter medium bellows at a first one of said end surfaces and an interior of said first filter medium bellows is completely closed off at said first one of said end faces, and wherein end faces of said first and said second filter medium bellows are seal-tightly connected to one another at a second one of said end surfaces.
 12. The filter insert according to claim 1, wherein said filter element is a compact air filter element with a plurality of passages that are closed off alternatingly at said end surfaces.
 13. The filter insert according to claim 1, wherein said filter element is a rectangular zigzag-folded filter element and wherein said end surfaces are formed by fold edges.
 14. A filter insert comprising: a filter element with an end surface at an inlet side and an end surface at an outlet side; a frame circumferentially extending about lateral sides of said filter element and connected to said filter element; an axial seal supported on said frame, wherein said seal is adapted to be pressed against a sealing surface of a filter housing in a sealing direction; said frame having on two opposite lateral sides of said filter element a first contact surface and a second contact surface for clamping the filter insert by a first clamping element and a second clamping element in the filter housing; wherein normals of said contact surfaces are oriented substantially opposite to said sealing direction; said first contact surface having a first profile of varying height and said second contact surface having a second profile of varying height that is different from said first profile of varying height; wherein the filter insert is clamped by said first and second clamping elements having a counter profile, respectively, relative to said first and second profiles of varying height in the filter housing.
 15. The filter insert according to claim 14, wherein a height of said profiles of varying height is defined by a spacing of sections of said first and second contact surfaces from a plane defined by said seal.
 16. The filter insert according to claim 15, wherein said profiles of varying height along said two opposite lateral sides have a common preferred direction along which said profiles of varying height extend and across which said height primarily increases, wherein the increase of said height is continuous or stepwise.
 17. The filter insert according to claim 16, wherein said preferred direction is a mounting direction of the filter insert for insertion into the filter housing.
 18. The filter insert according to claim 16, wherein said two opposite lateral sides are substantially planar or slightly elliptical.
 19. The filter insert according to claim 16, wherein said frame in an area of said two opposite lateral sides has at least one groove that extends parallel to a plane defined by said seal between said plane of said seal and said first and second contact surfaces and undercuts in a direction opposite to said preferred direction a portion of said profile of varying height.
 20. The filter insert according to claim 14, wherein said frame comprises an annular end disk and is arranged at said end surface at said inlet side or said end surface at said outlet side, wherein said annular end disk covers partially said end surface and provides a flow-through opening, wherein said seal is arranged on said annular end disk, wherein said annular end disk has an annular rib that extends partially or completely circumferentially within an area of said annular end disk inside said seal, wherein said annular rib projects away from said annular end disk and intercepts a surface that is defined by an engagement surface of said seal in an unclamped state of said seal.
 21. The filter insert according to claim 20, wherein said frame at a level of said annular end disk has a first and a second guiding projections that project in a mounting direction of the filter insert.
 22. The filter insert according to claim 20, wherein said filter element has at least two spacer knobs of elastic material on said lateral sides at an end opposite said frame.
 23. The filter insert according to claim 14, wherein said filter element comprises at least one annular star-shaped folded filter medium.
 24. The filter insert according to claim 14, wherein said filter element comprises a first and a second annular star-shaped folded filter medium bellows, wherein said first filter medium bellows is smaller than said second filter medium bellows and is arranged concentrically inside said second filter medium bellows, wherein said frame is seal-tightly connected to said second filter medium bellows at a first one of said end surfaces and an interior of said first filter medium bellows is completely closed off at said first one of said end faces, and wherein end faces of said first and said second filter medium bellows are seal-tightly connected to one another at a second one of said end surfaces.
 25. The filter insert according to claim 14, wherein said filter element is a compact air filter element with a plurality of passages that are closed off alternatingly at said end surfaces.
 26. The filter insert according to claim 14, wherein said filter element is a rectangular zigzag-folded filter element and wherein said end surfaces are formed by fold edges.
 27. A filter device comprising: a filter insert according to claim 1 or 14; and a filter housing having an inlet area and an outlet area for a medium to be filtered, wherein said inlet area or said outlet area has a receiving area with an annular sealing surface that matches said seal of said filter insert.
 28. The filter device according to claim 27, further comprising a lid, wherein: said filter housing has a mounting opening through which said filter insert is insertable in a mounting direction that is perpendicular to a main flow direction into said filter housing; said mounting opening is closable by said lid; said lid comprises a first and a second clamping brackets that project into said filter housing, wherein said first clamping bracket extends across a first lateral side of said filter insert and said second clamping bracket extends across a second lateral side of said filter insert; said first and second clamping brackets each have clamping surfaces oriented in a direction of said receiving area; wherein said clamping surfaces each have a profile of varying height, wherein said profiles of varying height of said first and second clamping surfaces match said profiles of varying height of said contact surfaces on said frame and form a matching shape, respectively; when said lid is mounted and said first and second clamping brackets project completely into said filter housing, said first and second clamping brackets apply a force onto said contact surfaces of said filter insert in such a way that said seal of said filter insert is pressed against said sealing surface of said filter housing and said filter insert is positionally secured in said filter housing.
 29. The filter device according to claim 28, wherein said filter housing has housing sidewalls with two expanded housing sections that each have a planar support surface facing said receiving area, wherein said first and second clamping brackets have planar support surfaces opposite said clamping surfaces and wherein said planar support surfaces of said first and second clamping brackets rest on said planar support surfaces of said expanded housing sections.
 30. The filter device according to claim 28, wherein said filter housing has at least one rib that is arranged on a housing sidewall of said filter housing and beginning at a bottom of said filter housing extends in a direction toward said mounting opening, wherein said at least one rib is designed such that, upon mounting of said filter insert, said at least one rib engages a groove of said filter insert.
 31. The filter device according to claim 28, wherein said filter housing has two opposed housing sidewalls each provided with a ramp having a ramp surface that is oriented in a direction toward said receiving area, wherein a spacing of said ramp surface relative to a receiving surface of said receiving area is reduced in said mounting direction, wherein guiding projections of an end disk of said filter insert upon mounting of said filter insert are guided by said ramp surfaces in a direction toward said receiving area, wherein said filter insert is positioned such that a rib of said filter housing engages a groove provided on said filter insert.
 32. The filter device according to claim 28, wherein said mounting opening on a side where said frame of said filter insert is received is cut deeper into a housing sidewall of said filter housing than in an area where an end of said filter insert opposite said frame is received.
 33. The filter device according to claim 28, wherein said filter housing has an opening inside said sealing surface, wherein said opening is designed such that said opening surrounds an annular rib, extending partially or completely on an end disk of said filter insert, when said filter insert is completely inserted in said mounting direction into said filter housing.
 34. A product group of filter devices according to claim 28, comprising housing variants of said filter housing; lid variants of said lid; and filter insert variants of said filter insert; wherein different filter elements have correlated therewith a combination of the following features: a. the groove of said filter insert is provided on none of, on one of, or both of said lateral sides; b. the rib of said filter housing is provided on none of, one of, or both of said housing sidewalls; c. at least one of said clamping surfaces and said contact surfaces of said filter insert has a profile of varying height that differs from a profile of varying height of other filter devices of the product group. 